Stoker control sxstem



Dec. 24, 1946.

F. 5. DENISON STOKER CONTROL SYSTEM Filed April fr, 19:58

Patented Dec. 24, 1940 2,226,293 s'roKEncoN'rRoL SYSTEM Frederick S.Denison, Minneapolis, Minn., assignor to Minneapolis-Honeywell RegulatorCompany, Minneapolis, Minn., a. corporation of Delaware ApplicationApril 7, 1938, Serial No. 200,744.

8 Claims.

My invention relates to automatic control of solid fuel feeding devicesin heating systems and is more particularly concerned with a noveltiming apparatus for periodically operating the fuel feeding device forshort intervals to maintain a lire when no heating is being required.

In the past it has been necessary to 'employ clock mechanisms tosatisfactorily time the operation of automatic fuel feeding devices suchas lo stokers so as to prevent furnace fires from going out during mildweather when the periods between thermostatic calls for heat arerelatively long. Clock movements and electrical clock timers and thelike While satisfactory forthe l5 purpose are also relatively expensiveand are more or less delicate in construction. I have invented' apneumatic timing device of very rugged and inexpensive constructionwhereby I can accurately and automatically time stoker operal tionwithout the need of clocks or the like and therefore resulting in asubstantial reduction in iirst cost of apparatus of this type while atthe same time securing increased reliability.

The objects of my invention are:

The provision of a timing device comprising a pneumatic chamber havingpressure release means and whereby time may be measured by theexhausting of pressure from within the cham` ber.

3o The provision of a timing device comprising a pneumatic lchamberhaving a collapsible portion and a releasing port for air or the like soarranged that time may be measured by the position of the collapsibleportion as it collapses due to release of air through the port.

. The provision of a-timing device4 comprising a diaphragm chamberadapted to contain pressure and means for releasing the pressurerelatively slowly, the diaphragm sinking upon re- 4o1 lease of pressureand arranged to actuate a switch or the like after a predetermined timedepending on the pressure.

The provision, in combination with an automatic stoker, of a pneumatictiming device comprising a pneumatic chamber having means re sponsive tothe pressure therewithin and means for controlling the stoker actuatedby the presn sure responsive means, the said means being operable tomeasure time based on the rate oi eX- haustion of air or the like fromthe chamber.

The provision, in combination with an auto matic Stoker system and afurnace draft fan, of a pneumatic timing device comprising a dian phragmchamber having a diaphragm adapted 5u to be lifted by draft from theian, and a switch in control of the Stoker and actuated at the er.lmpiration of predetermined time intervals determined by the rate ofrelease oi air from below the diaphragm. do 'it will be understood thatmy invention is not limited to stoker control systems but may be pemployed in various other timing capacities. The exact nature of myinvention will become clear as my specification proceeds, the inventionresiding in the construction, and arrange- 5 ment of parts, as well asin the various combinations upon which I desire protection by LettersPatent of the United States and towards which I have directed the claimsappended hereto. l0

lReferriliato the drawing I have'lndicated my imprcjs'ved timing devicegenerally at I. In a preferred embodiment of the invention I have shownthe device comprising a diaphragm chamber formed of an upper circular,more or less l5 dome shaped member 2 and a lower member 3 also circularand having a cross sectional configuration as shown. The members 2 and 3have peripheral flanges 4 and 5, respectively. Numeral E indicates ailexible diaphragm made of 2o leather or other similar material andhaving its peripheral portions interposed between the anges 4 and 5, theflanges being secured together by bolts 'l with edge portions of thediaphragm in sealing engagement therebetween. 25

The member 3 has a depressed portion it in screw threaded relation withwhich is a guide li for a plunger i2. The plunger I2 is connected by astein It with a diaphragm il. The stem I3 may have an integral disc Itdisposed adja= 30 cent the diaphragm 6 and connected to a disc backingmember I5 disposed on the opposite side of the diaphragm 6. Preferablythe end of stem I3 extends through the diaphragm 6 and disc I5 and has aretaining washer I6 or the like 35 secured to its end adjacent the discI5.

Within the depressed portion Ill is a mercury switch 20 mounted on alever arm 2i pivoted to a lug 22 upstandlng from the lower surface ofthe depressed portion III. The lever arm 2l is 40 movable between stops23 and `2li formed integrally with the portion I0 and is biased towardseither one stop or the other by an overcenter coil spring 25 attached tothe lever arm and to a side wall ofthe depressed portion lil as shown.45 The left end oi the lever arm iii is forked or bifurcated and thestem it is engaged between the prongs or bifurcations. The diaphragm tof my device is adapted to rise and iall moving the stem it and plungeri2 vertically. The diain 50 phragm t may lift the stem lil until theplunger i2 engages the end of the lever arm :il raising it until theove'rcenter spring @it snaps the lever arm against the stop 23 into theposition shown on the drawing.- ln this position the mercury switch isopen as shown. The diaphragm t; may settle until the portion ci stemiii-larger die ameter adjacent disc it engages the end ci? lever arm it?moving it downwardly until the overeen ter spring snaps the lever aimthe stop 24 in which position the mercury switch 20 is closed.

'Il'he member 3 has a boss 21 having needle valve 28 therein. A tube 29communicates-with the inlet of the needle valve and the outlet of theneedle valve' communicates with the space below the diaphragm 6 througha swing check valve 30 disposed in a recessed portion 3| on the innerside of the member 3. The swing check valve cooperates with a shoulderforming a seat at the inner end of the outlet port of the needle valve28. When air pressure is supplied through the tube 29 in a manner whichI will later describe it passes through the needle valve 28, the swingcheck valve 30 and into the diaphragm chamber lifting the diaphragm 6 toa raised position.

The member 3 has a second boss 32 having a needle valve 33 disposedtherein. The needle valve 33 forms a release for fluid pressure from`below the diaphragm 6, the needle valve having a port 34 communicatingwith the interior of the member 3 and a port 35 communicating with theatmosphere. Both the needle valves 28 and 33 may be manually adjusted soas to vary the rate of pressure flow therethrough.

My invention is particularly adapted to but not limited to the controlof an automatic stoker of the type conventionally used in heatingsystems employing solid fuel. I have disclosed my invention incorporatedin a system of suchtype. Referring again to the drawing, numeral 40indicates a furnace fed with a solid fuel by an automatic electricallydriven stoker indicated at 4|. The stoker 4| may be of conventionalconstruction and I have chosen to disclose it as of the type including aforced draft fan 42 driven by the same motor which drives the stoker.'I'he draft fan 42 communicates with the combustion chamber of thefurnace through a forced draft duct 43. One end of the tube 29previously referred to communicates with a duct 43 as shown.

The system may be primarily controlled by a room thermostat or likedevice generally indicated at 44. The thermostat 44 may be of theconventional bimetallic element type having a movable switch arm 45cooperating with a fixed electrical contact 46 and a permanent magnet 41whereby the thermostat acts with a snap action to make and breakengagement between the blade 45 and contact 46. Power for the system maybe supplied from line conductors 41 and 48 connected to an externalsource of power, not shown. In the particular system which I havedisclosed I employ line voltage in all circuits but it is to beunderstood that I may use relays as often employed in thermostaticallycontrolled electric circuits and the like.

'I'he manner of control of the stoker 4| and blower 42 by thethermostatA 44 will be obvious to those skilled inthe art. Whenever thetemperature to which the thermostat 44 is responsive falls to apredetermined value for which it is set, blade 45 will engage fixedcontact 46 completing a circuit through thev stoker and blower motor asfollows: from line conductor 41 through a wire 49 to the thermostat,through blade 45, fixed contact 46, wire 50, the stoker and blower motorand wire 5| back to line conductor 48: Whenever blade 45 disengages fromfixed contact 46 the above circuit is broken and the stoker and blowermotor stops.

In systems of the type disclosed, especially intervals betweenthermostatic calls for heat and consequent operations of the stoker.During these intervals provision must be made to keep the fire alive,otherwise upon the next thermostatic call for heat the fire may be outand raw coal will be fed onto a cold fuel bed.v The function of myinvention is to intermittently operate the stoker at timed intervals tosupply sufficient fuel to keep the flre alive during the above describedrelatively long intervals when the thermostat is not calling for heat.

Whenever the Stoker 4| and blower 42 are operated pressure will beforced through the duct 43 and tube 29 to the interior of the diaphragmchamber causing diaphragm 6 to be lifted, tilting the mercury switchinto the position shown,

Iin the manner which I have already described.

tire amount necessary to tilt the mercury switch.

20 into the position shown. As long as the blower 42 is operated thediaphragm is maintained in its lifted position inasmuch as the bleed offluid pressure through the needle valve 33 is considerably slower thanthe rate at which air pressure is forced through the needle valve 28. Assoon as the blower 42 stops the swing check valve 30 is pressed rmlyagainst its seat by reason of the pressure within the diaphragm chamberand the pressure now bleeds off through the needle valve 33. As thepressure bleeds off the diaphragm 6 gradually starts moving the stem |3and plunger |2 downward accordingly. After a predetermined time of, forexample, thirty minutes which may be adjusted by adjusting the positionof the needle ivalve 33, the portion of the stem |3 of larger diameterwill engage lever arm 2| and the mercury switch will be tilted to closedposition in the manner already described. As soon as the mercury switch20 is closed a circuit for the stoker and blower motor will be completedas follows: from line conductor 41 through wire 49, a wire 52 throughthe mercury switch 20, a wire 53, wire 50 to the stoker and blower motorand wire 5| back to the line conductor 48. As soon as the motor startsair pressure will again be forced through the tube 29 lifting thediaphragm 6. After a predetermined time as mentioned above which may betwo or three minutes for example according to the adjustment of needlevalve 28 the diaphragm 6 will-have been lifted sufiiciently to open themercury switch 20 stopping the motor. Thus it will be seen that when thethermostat 44 does not call for heat the stoker and blower motor areoperated for short periods at predetermined intervals of time so as tdkeep the fire in the furnace alive.

From the foregoing it should be apparent to those skilled in the artthat I have provided a unique timing device and have combined it withthe other elements of my disclosure in a novel manner for producingresults having manifest utility and value. My device is not of thedelicate construction characteristic of most heretofore known timingdevices but on the other hand is of very sturdy construction and iscomprised of parts none of which are likely to get out of order oradjustment. Adjustments of the duration of firing periods and also theinterval of time between them may be satisfactorily made and with theutmost simplicity merely by adjusting the needle valves 28 and 33 with ascrew driver.

My device is of extremely economical construction and is of such anature that it may be infore dispensing with the need of skilled servicemen.

I have disclosed one preferred embodiment of v my invention and oneapplication thereof which in this particular instance is a stokercontrol system. 'I'here are many other forms and modifications which myinvention may take and many changes therein and applications thereofwill occur to those skilled in the art. I therefore intend that mydisclosure be interpreted only as illustrative and that the scope of myinvention be limited only as determined by the appended claims.

I claim as my invention:

1. In a heating control system, in combination, an automatic stoker andforced draft means, a thermostat controlling said stoker and forceddraft means, a timing device for intermittently operating the stoker formaintaining the fire when no heating is needed comprising a diaphragmchamber having a diaphragm therein, means for forcing draft airunderneath the diaphragm to lift it when said forced draft means ispperating, means for relatively slowly releasing the pressure below thediaphragm permitting it to settle when said forced draft means is notoperating, and a switch actuated by said diaphragm and controlling saidstoker and forced draft means.

2. In a temperature control system, in combination, an automatic stokerand forced draft means for a furnace, temperature responsive means forcontrolling said Stoker and forced draft means, a timing device forcontrolling said Stoker and forced draft means to maintain a fire whenno heating is necessary, said device comprising a chamber having amovable Wall portion operable to actuate a switch controlling saidvstoker and forced draft means, means including an adjustable valvewhereby forced draft moves said movable Wall portion in a direction tostop said Stoker and forced draft means, and means including anadjustable release valve `whereby said movable wall moves in a directionto start said stoker and forced draft means when fluid is not beingforced by said last means.

3. In a heating system, in combination, an automatic Stoker and forceddraft means, temperature responsive means for controlling the Stoker andforced draft means comprising a fan, said forced draft means stoppingwhenever the stoker is stopped by the temperature responsive means, atiming device for operating the stoker irrespective of the temperatureresponsive means, said device comprising a chamber having an expansiblewall member adapted tobe expanded by draft from the fan Whenever the fanoperates, said chamber having a release port for releasing air therefrompermitting the chamber to contract when the fan stops, and meansoperably associated with the expansible wall member for controlling theStoker.

4i. In a combustion system, in combination, an automatic Stoker andforced draft means, automatic means for controlling the stoker andforced draft means, said forced draft means supplying air for combustionof fuel supplied by said stoker, said automatic means comprising atiming device for controlling said Stoker, said device comprising achamber having an expansible `wall member adapted to be expanded bydraft from the forced draft means, said chamber being adapted tocontract upon release of air therefrom, and means operably associatedwith the expansible wall member for controlling the stoker.

5. In a combustion system, in combination, means adapted to form acombustion chamber, means for supplying fuel to said combustion chamberand means for supplying draft air thereto, automatic means in control ofsaid fuel supply means comprising a device forming an expansiblechamber, means whereby draft air may be communicated to said expansiblechamber, said chamber having a movable wall member adapted to beexpanded by draft from the forced draft means, said chamber beingadapted to contract upon release of air therefrom, and means actuable bythe movable Wall member for controlling the fuel supply means, saidchamber having a restricted air passage communicating therewith so thata relatively long period of time is required for said movable wallmember to move sufficiently to actuate said means controlling the fuelsupply means.

6. In a heating system, in combination, an automatic stoker and forceddraft means comprising a fan, temperature responsive means controllingthe stoker and forced draft means, said forced draft means stoppingwhenever the stoker is stopped by the temperature responsive means, atiming device for operating the stoker irrespective of the temperatureresponsive means, said device comprising a chamber having an expansiblewall member adapted to be expanded by draft from the fan Whenever thefan operates, said chamber having a release port for releasing airtherefrom permitting the chamber to contract when the fan stops, andmeans operably associated with the expansible wall member for startingthe stoker when the said wall member has assumed a predeterminedposition upon contraction of the chamber.

7. In a combustion system, in combination, an automatic stoker andforced draft means, condition responsive means for controlling theStoker and forced draft means, and automatic means for operating thestoker at intervals to maintain limited combustion during periods whencombustion is not demanded by the condition responsive means, saidautomatic means comprising a pneumatic timing device operated by draftair supplied by said forced draft means, said device being in the formof a chamber having an expansible wall portion and means having arestricted orifice for slowly releasing air from said chamber.

8. In a heating system, in combination, an automatic stoker and forceddraft means, condition responsive means for controlling the stoker andforced draft means, a device for controlling the operation of thestoker, said device comprising means forming a chamber having anexpansion wall portion, means having a restricted orifice whereby draftpressure supplied by said forced draft means is communicated to saidchamber, means actuable by said expansible wall portion to initiateoperation of said Stoker after a variable interval of time followingstoppage thereof, which interval is dependent upon the length of timethat draft pressure is communicated to said chamber. v

FREDERIG S. DENISON.

istY

